Manufacturing Thin Film Solar Panels
Two criteria must be primarily satisfied for manufacturing thin film solar cells. One is to find a proper substrate, and the second to select a poly-Si thin film layering or depositing technique.
In order to meet the above requirements, SSP (Silicon Sheets from Powder) equipment and RTCVD (Rapid Thermal Chemical Vapor Deposition) system installations are done.
Countries like China are the leading producers of metallurgical Si powder. This is exported and sold at very low costs, and thus becomes significantly beneficial for the easy preparation of SSP for manufacturing poly-Si thin film solar panels.
10% efficiency may not look very impressive, however for developing countries, it can be very helpful considering the huge costs involved with the manufacturing of the higher efficiency counterparts.
Let’s try to understand the basic ingredients that make up the basic structure of a poly-Si thin film solar cell over SSP through the following discussion. Looking at the figure alongside, we see that it’s typically made up of 5 discrete layers viz:
- The uppermost contact made up of Indium Tin Oxide (ITD)
- The thin N-type doped section (green color), and the rather prominent P-type doped section (red color) also called the epitaxy layer
The intermediate base material P+SSP substrate and the extreme back contact shown in yellow color.
The above explained structure of SSP layer has three fundamental functions:
- To self support the operation of the device
- Carrying out crystal seed growth for the epitaxial layer and
Maintain BSF or back surface field for enhancing the properties of the solar cell (open circuit voltage VOC)
In the process of manufacturing firstly over the SSP base the epitaxial layer is made through RTCVD (hopefully in the future the intermediate layers will also include material like SiO2 to improve solar cell efficiency), after that the pn junction is introduced by a diffusion process.
The ITO contact elements are fixed through a process of vacuum evaporation and finally an antireflection cover of SiNX film is coated over the surface through PECVD.
After concluding the above process, the SSP ribbon is subjected to the following procedures:
- Silicon powder is heavily injected and packed continuously over the quartz carrier plates by electric motor
The upper surface powder of the layer is introduced to a temperature of about 14120 Celsius and is zone melted in a special Ar atmosphere through high intensity line focused halogen lamps
- The remaining silicon powder gets combined with the molten liquid during the process of re-crystallization
The above manufactured solar cell ribbon is very thin typically 0.6 to 1mm in thickness (depending upon the silicon powder particle size) and 60 to 110mm wide and normally the length is about 1000 to 1500mm.
The finished product is sleek, flexible, rollable, and perfectly suited as thin film solar roof panels.
Wondering where to buy these thin film solar panels? Perhaps the list of manufacturers provided here should help.